The HTTP 406 Error is returned when require SSL flag is turned on in Admin settings, RhodeCode checks if request comes from an SSL enabled server (by checking some headers), if you know that you have only SSL http server in front of it you can turn off this check, or make sure you send
proper HTTP_X_URL_SCHEME,HTTP_X_FORWARDED_SCHEME, HTTP_X_FORWARDED_PROTO
Headers
Cheers